Behind the Headlines: Does diet affect mental health?

A significant rise in the number of patients suffering mental illness over the past 60 years is down to the increasingly bad British diet, according to media reports.

Growing evidence of links between diet, brain and behaviour has led experts to conclude that modern diets could cause depression, attention deficit hyperactivity disorder (ADHD) and Alzheimer's disease.

The media stories were based on a pair of reports published this month by charities the Mental Health Foundation, which supports patients with mental illness, and Sustain, which campaigns for healthier food and more sustainable farming.

The reports used the same evidence but while Sustain concluded that good nutrition was necessary for a healthy brain and mind, the Mental Health Foundation linked poor diet and mental health problems more explicitly.

What is in the reports?

The reports included physiological evidence for a link between diet and the brain, as well as epidemiological evidence showing that diet affected mental state.

They cited studies showing that 20 per cent of the brain was made up of essential omega-3 and omega-6 fatty acids that could only come from the diet and that some neurotransmitters could only be synthesised from other essential nutrients.

They also reported a study showing that low fish intake was associated with high levels of depression, research suggesting an association between fat consumption and Alzheimer's, and a study showing that certain food additives might trigger ADHD.

The Mental Health Foundation also surveyed 2,122 people aged over 15 about their diet and mental health.

They found that younger people generally ate less well than older people.

They also found that people with 'daily' mental health problems ate less fresh fruit and vegetables, while people with 'some experience' of mental health troubles ate more fatty, sugary and processed food.

Both reports noted that the quality of the UK diet had deteriorated over the past 60 years. Vegetable consumption has declined by 34 per cent and fish consumption by 59 per cent.

What do the authors say?

Courtney van de Weyer, project officer at Sustain, gathered the evidence for both reports. She acknowledged that more research was needed but said there were clear links.

She said diet could be used as a treatment for mental health problems: 'There are a number of randomised double-blinded controlled trials for particular supplements. The positive effects of essential fatty acids on depression is a good example.'

Dr Andrew McCulloch, chief executive of the Mental Health Foundation, said the reports empowered patients in the care of their mental health.

'The government must look to nutrition as an option in helping to manage people's mental health problems,' he said.

What do other experts say?

Claire MacEvilly, a nutritionist at the Medical Research Council human nutrition unit in Cambridge, said that although good epidemiological studies looked at links between diet and mental health, only a few intervention studies demonstrated that a good diet helped mental illness.

'It's not a case of eat more wholegrains and fruit and vegetables and mental health symptoms will go away,' she said.

However, she did not dispute that good nutrition could benefit patients with mental illness.

Kate Williams, a dietitian and spokeswoman for the British Dietetics Association, said links between diet and mental illness were unsupported but there was evidence that nutrition was a contributing factor.

She said that GPs should consider a patient's diet if they presented with mental problems.

'A balanced diet as recommended by health professionals is important for your brain and the rest of your body,' she said.

Dr David Osborn, a consultant psychiatrist at UCL with a research interest in schizophrenia, said nutrition could be an adjunctive treatment for mental illness, but not a direct therapy, and would benefit patients' physical and mental health.

'Schizophrenics in particular make bad dietary choices, which could contribute to increased cardiovascular risk,' he said.

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